1. Field of the invention.
This invention relates to plunging constant velocity universal joints.
In particular the invention is concerned with a plunging constant velocity universal joint of the kind (hereinafter referred to as the kind specified) comprising a hollow outer member and an inner member which are formed with pairs of opposed longitudinally extending grooves, torque transmitting balls which are each engaged in and between a pair of said grooves in the inner and outer members and are movable along the grooves to permit relative angular and axial (plunging) movement between the members, and a ball cage which is located between the inner and outer members and is formed with apertures in which the balls are located, the cage being operative to assist in maintaining the balls in the bisector plane of the joint thereby to provide the constant velocity ratio characteristics of the joint.
2. Description of the prior art.
A disadvantage of universal joints of the kind specified is that some skidding of the balls takes place during plunge.
In order to overcome this disadvantage, it has previously been proposed in a universal joint of the kind specified to provide for axial movement of the cage relative to both the inner and outer joint members so that the cage is not constrained to move axially with either of the members but is free to follow the movement of the torque-transmitting balls during plunge. In all the previously proposed arrangements skidding of the balls is prevented in this way over substantially the whole range of permitted plunging movement.
For example, in our U.S. Pat. No. 3,452,558 there is provided a constant velocity universal joint which is of the kind specified, having a guide member which is free to move axially of the inner member and is attached either to the cage or to the inner member and has a convex part-spherical surface which engages in, and allows angular movement of the guide member with respect to, the other of these two members, i.e. the inner member of the cage, to control movement of the cage which is also controlled by way of a part-spherical external surface on the cage which engages a cylindrical bore in the outer member or a member fixed thereto, said part-spherical surfaces having centres of curvature which are offset by a substantially equal amount on opposite sides of the joint centre along the joint axis with the centre of the part-spherical surface on the guide member always positioned on the rotational axis of the inner member.
In all the embodiments described and illustrated in U.S. Pat. No. 3,452,558 the guide member is axially movable relative to the inner member to an extent sufficient to prevent skidding of the balls over substantially the whole range of permitted plunging movement.
A drawback of the previously proposed arrangements is that the provision for axial movement of the cage relative to the inner and outer members of the joint over substantially the whole range of permitted plunging movement imposes limitations on the various design considerations which are desirably taken into account when designing universal joints.